As MEMS devices and MEMS systems are widely used in the field of automobile and consumer electronics, and through-silicon via (TSV) etch technology has wide prospect in the field of packaging, plasma deep silicon dry etching process gradually becomes one of the most important processes in the field of MEMS manufacturing and TSV technology.
Deep silicon etching process is different from a general silicon etching process in that: etching depth of the deep silicon etching process is much larger than that of the general silicon etching process and is generally several tens of micrometers or even up to one hundred meters, and however etching depth of the general silicon etching process is smaller than 1 micrometer. In order to etch a silicon material of several tens of micrometers, the deep silicon etching process is required to have a larger etching rate, a higher selection ratio and a larger aspect ratio.
Currently, a popular deep silicon etching process is Bosch process invented by Bosch in Germany or improvements on it. The main features of Bosch process are: the whole etching procedure is multiple repetitions of one circulation unit and the circulation unit includes an etching operation and a deposition operation, that is, the whole etching procedure is alternate circulation of the etching operation and the deposition operation. Process gas used in the etching operation is SF6, which allows a higher etching rate of a silicon substrate. In practical application, since the etching procedure is isotropic etching, it is difficult to control sidewall morphology. So, in order to avoid etching of the sidewall, the deposition is incorporated in the whole etching procedure to deposit a layer of polymer protection film on the sidewall to protect the sidewall from being etched, so as to etch only in the vertical direction.
The defects in the prior art are: since the etching operation and the deposition operation are performed alternately, the polymer deposited on the sidewall of the etched section is not smooth, and so the product resulted from such an etching is not ideal.